Method for the preparation of composite membranes based on interpenetrating polymer networks

Abstract

Semipermeable composite membranes which comprise an interpenetrating polymer network may be prepared by reacting polyethylene glycol with a toluene diisocyanate to form an isocyanate-capped polyether, thereafter admixing the isocyanate-capped polyether with a heterocyclic nitrogen-containing compound to form an interpenetrating polymer network membrane-forming composition, forming a film of the composition on a porous support backing material and curing the resultant composite in a hydrous atmosphere to generate an amine-capped polymer, and subsequently reacting a portion of the isocyanate groups present to form a substituted polyurea which will physically enter the heterocyclic nitrogen-containing compound in the membrane.

We claim as our invention: 
     
       1. A process for the production of a composite semipermeable interpenetrating polymer network membrane which comprises reacting a polyether with an isocyanate to form an isocyanate-capped polyether, admixing said isocyanate-capped polyether with a heterocyclic nitrogen-containing compound selected from the group consisting of polyvinylpyridine and mixtures of polyvinylpyridine and poly(N-vinylpyrrolidone) to form an interpenetrating polymer network membrane-forming composition, forming a film of said composition on a porous support backing material, curing the resultant composite in a hydrous atmosphere at curing conditions for a time sufficient to generate an amine-capped polymer by hydrolysis of a portion of said isocyanate-capped polyether with said amine-capped polymer subsequently reacting with a portion of the isocyanate groups present in said composition to form a substituted polyurea which serves to physically entwine said heterocyclic nitrogen-containing compound in said composition, and recovering the resultant composite semipermeable interpenetrating polymer membrane. 
     
     
       2. The process as set forth in claim 1 in which said curing conditions include a temperature in the range of from about ambient to about 100° C. and a period of time in the range of from about 5 minutes to about 48 hours. 
     
     
       3. The process as set forth in claim 1 in which said hydrous atmosphere possesses a relative humidity in the range of from about 20% to about 100%. 
     
     
       4. The process as set forth in claim 1 in which said polyether is selected from the group consisting of polyethylene glycol, polypropylene glycol and block copolymers of ethylene glycol and propylene glycol. 
     
     
       5. The process as set forth in claim 1 in which said isocyanate is selected from the group consisting of toluene diisocyanate, methylene diphenylisocyanate, ethylene diphenylisocyanate, and propylene diphenylisocyanate. 
     
     
       6. The process as set forth in claim 1 in which said isocyanate-capped polyether and said heterocyclic nitrogen-containing compounds are present in a weight ratio in the range of from about 1:1 to about 8:1 isocyanate-capped polyether to heterocyclic nitrogen-containing compound. 
     
     
       7. The process as set forth in claim 1 in which the polyvinylpyridine and poly(N-vinylpyrrolidone) are present in said mixture in a weight ratio in the range of from about 1:2 to about 4:1 polyvinylpyridine to poly(N-vinylpyrrolidone). 
     
     
       8. The process as set forth in claim 1 in which said porous support backing material is polysulfone. 
     
     
       9. The process as set forth in claim 1 in which said porous support backing material is polyethylene. 
     
     
       10. The process as set forth in claim 1 in which said heterocyclic nitrogen-containing compound is poly(2-vinylpyridine). 
     
     
       11. The process as set forth in claim 1 in which said heterocyclic nitrogen-containing compound is poly(4-vinylpyridine). 
     
     
       12. The process as set forth in claim 1 in which said polyether is a block copolymer of ethylene glycol and propylene glycol, said isocyanate is toluene diisocyanate, said heterocyclic nitrogen-containing compound is poly(4-vinylpyridine) and said porous support backing material is polysulfone. 
     
     
       13. The process as set forth in claim 1 in which said polyether is polypropylene glycol, said isocyanate is methylene diphenylisocyanate, said heterocyclic nitrogen-containing compound is poly(2-vinylpyridine) and said porous support backing material is polysulfone. 
     
     
       14. The process as set forth in claim 1 in which said polyether is polyethylene glycol, said isocyanate is toluene diisocyanate, said heterocyclic nitrogen-containing compound is a mixture of poly(4-vinylpyridine) and poly(N-vinylpyrrolidone) and said porous support backing material is polysulfone. 
     
     
       15. The process as set forth in claim 1 in which said polyether is a block copolymer of ethylene glycol and propylene glycol, said isocyanate is ethylene diphenylisocyanate, said heterocyclic nitrogen-containing compound is a mixture of poly(2-vinylpyridine) and poly(N-vinylpyrrolidone) and said porous support backing material is polyethylene. 
     
     
       16. The process as set forth in claim 1 in which said polyether is polyethylene glycol, said isocyanate is propylene diphenylisocyanate, said heterocyclic nitrogen-containing compound is poly(4-vinylpyridine) and said porous support backing material is polyethylene.